In the course of use regulations and emission rules for internal combustion engines, that are becoming stricter, the recording of measured variables in the combustion chamber of an internal combustion engine is becoming more important all the time. An example for this is a so-called combustion chamber pressure sensor, with the aid of which, among other things, the combustion process may be monitored and controlled.
In order to be able to install such sensors, at the least space requirement and without changes in the internal combustion engine, for example, pressure sensors in the form of piezoceramic elements or of quartz are integrated into the spark plug of an internal combustion engine. The load generated in the piezoceramic element or the quartz is proportional to the impressed pressure in the combustion chamber. Since these sensors generate an output signal by their high impedance, which cannot be simply transmitted to the engine control unit, a signal conversion is required. This signal conversion usually takes place by a load amplifier or an impedance converter. The semiconductor components required for this are generally not able to be accommodated in the spark plug.